Report maximum and available volume counts for a scheduler pool

Report the number of volumes currently in a scheduler pool and the maximum amount allowed to the scheduler so that volume creates are not provisioned onto a host that has reached its max volume count. Reported to the scheduler in a way like below:

capability = {
    ..
             'pools': [
                {'pool_name': '1st pool'
                 'total_capacity_gb': 500,
                 ...
               -->'max_volume_count': 256,
               -->'current_volume_count': 120,
               -->'number_of_available_volumes': 136,
]}